Introduction

The Boost.Signals2 library is an implementation of a managed
signals and slots system. Signals represent callbacks with multiple
targets, and are also called publishers or events in similar
systems. Signals are connected to some set of slots, which are
callback receivers (also called event targets or subscribers), which
are called when the signal is "emitted."

Signals and slots are managed, in that signals and slots (or,
more properly, objects that occur as part of the slots) can track
connections and are capable of automatically disconnecting signal/slot
connections when either is destroyed. This enables the user to make
signal/slot connections without expending a great effort to manage the
lifetimes of those connections with regard to the lifetimes of all
objects involved.

When signals are connected to multiple slots, there is a
question regarding the relationship between the return values of the
slots and the return value of the signals. Boost.Signals2 allows the
user to specify the manner in which multiple return values are
combined.

Signals2

This documentation describes a thread-safe variant of the
original Boost.Signals library. There have been some changes to
the interface to support thread-safety, mostly with respect to
automatic connection management. This implementation was written by
Frank Mori Hess. Acknowledgements are also due to Timmo Stange, Peter
Dimov, and Tony Van Eerd for ideas and feedback, and to Douglas Gregor
for the original version of Boost.Signals this effort was based on.